Method of securing shoe parts together



1,951,474 PATENT OFFICE IWETHOD 0F SECURING SHOE PARTS TO- GET HER

Fred C. Eastman, Marblehead Massa assignor to United Shoe Machinery Corporation, Paterson;

N. J., a corporation of New Jersey No Drawing. Application May 11, 1933, Serial No. 670,537

5 Claims.

This invention relates to improvements in the cementing together of pieces of stock by cellulose derivative cements, and is disclosed herein with reference to the cement attaching of soles to shoe uppers.

In the manufacture of shoes wherein the soles are cement attached to the uppers it has been the practice to apply pyroxylin cement to the overlasted marginal portion of the shoe upper and to the marginal portion of the attaching surface of the sole and to permit the cement to dry. The cement on one or both of the shoe parts subsequently has been activated or cut with a softener and the assembled shoe and sole placed under pressure which is maintained until the cement sets sufiiciently to hold the shoe parts together without the aid of such pressure. It has been common practice in the past to employ as the softening or activating composition one or more pyroxylin solvents having sufficiently high boiling points so that, after application to the hardened cement, the activating composition would volatilize slowly enough to permit ample time for the assembly of the shoe parts in juxtaposition under pressure. The use of such relatively high boiling solvents, however, has necessitated maintaining the shoe parts under pressure for relatively long periods of time, usually twenty minutes and upwards. This practice has been disadvantageous in requiring a relatively large number of premure applying devices for the production of a given number of shoes. Attempts to employ relatively volatile pyroxylin solvents as softening media, and which would permit the application of sole attaching pressure for much shorter periods, have met with another difliculty, namely, the solvent has evaporated before sufficient time has elapsed to accomplish the bringing of the shoe upper and'sole together and the application of pressure. The result has beenthe production of what are known as dry or starved joints.

An object of this invention is to provide an advantageous method of softening or activating hardened cellulose derivative cements. A further object is to provide a method of employing volatile solvents in sole attaching which will permit ample time to assemble the shoe parts after activation of the cement, and which will permit the removal of pressure from the assembled shoe parts within a suitably short time after the application of such pressure.

According to an illustrative embodiment of the invention, these and other objects are attained by employing a solvent composition which is relatively volatile at room temperature and chilling the composition until the vapor pressure thereof is reduced to such an extent that substantial evaporation thereof will not occur until ample time has elapsed to permit the assembly of the shoe parts, whereby the sole attaching pressure need be maintained for only a few minutes due to the rapidity with which the solvent composition dissipates after attaining room temperature. The chilling of the solvent composition may be accomplished by reducing the temperature of the solvent composition before, its application to a shoe part, or by reducing the temperature of a shoe part sufficiently to retard to the desired degree the evaporation of solvent composition applied thereto, or, in some cases, by chilling both the composition prior to application to a shoe part, and chilling also the shoe part to which the composition is applied.

The material employed to activate or soften the hardened cement may vary widely in composition, the invention not being limited in this respect. The composition may include substances which are in themselves solvents for pyroxylin and may contain compounds known as latent solvents which are not in themselves solvents but which possess solvent properties when mixed with other compounds. Additionally, the softener may, contain diluents and plasticizers. By way of example, suitable solvents for use individually or in combination in a softening composition are acetone (boiling point 565 C.), ethyl acetate (boiling'point 77 C.). Examples of latent solvents are diethyl ether (boiling point 35 0.), ethyl alcohol (boiling point 78.4" C.). iso-propyl ether (boiling point 675 0.), methyl alcohol (boiling point 66" C.). A suitable solvent composition which may be employed for the purposes of this invention is a mixture of 60 parts by weight of acetone and 40 parts by weight of diethyl ether. The ingredients of the softening composition will ordinarily be chosen to provide the desired solvent or softening effect on the pyroxylin cement and to provide the relatively high degree of volatility necessary to obtain the desired result of permitting the sole attaching pressure to be removed after a few minutes.

Where the solvent composition is to be chilled prior to its application to a cement-coated shoe part, such chilling may be readily carried out by disposing the composition in a container or compartment. maintained at a controlled low temperature, for example by amechanical efrigeration unit. Other expedients may be mployed, for example, packing the container of the softening composition in refrigerant such as ice or solidified carbon dioxide.

Chilling of the shoe parts themselves may be accomplished by storing the soles, or the lasted uppers, as the case may be, in a suitably refrigerated compartment until the time of use.

The extent to which chilling of the solvent composition is carried out, either by reducing the temperature of the composition priorto its application to a shoe part, or by reducing the temperature of the shoe part, or both, will be dependent upon the factors involved in the particular case, including the volatility of the softening composition itself, the time required to assemble the shoe parts to be cemented together, and the time available for maintaining the assembled parts under sole attaching pressure.

In carrying out my invention pyroxylin or other cellulose derivative cement may be applied, in accordance with prior practice, to the marginal areas of an outsole and to the overlastedmargln of a shoe upper. The cement is then permitted to dry or harden. Immediately prior to the sole attaching operation solvent is applied to one or both of the shoe parts, preferably to the hardened cement on the sole. The solvent composition may be chilled prior to such application, or may be applied to a chilled shoe part, or both. This application of softener may be accomplished manually as by means of a brush or may be accomplished by dipping the cemented surface of the sole into the softening composition as, for example, by a softener applying mechanism disclosed in application Serial No. 396,554, filed October 1, 1929, in the name of C. E. Hood. The sole and'shoe upper may then be brought into juxtaposition, and placed under pressure in a sole attaching machine, such as disclosed in United States Letters Patent No. 1,897,105, granted February 14, 1933, upon an application of Milton H. Ballard.

To illustrate by specific example the advantageous resultswhich may be accomplished by chilling the solvent composition according to' this invention: With a room temperature of 88 F., a temperature frequently encountered in summer weather in shoe factories, and employing a softening composition comprising in the neighborhood of 60 parts by weight of acetone and 40 parts of diethyl ether, the shoe parts and softening composition being at room temperature,

a period of about .12 seconds is available for the assembly of shoe parts after the application of the softening composition to the hardened cement on one of the shoe parts. Such assembly time in many cases is scarcely suflicient properly to assemble the shoe parts. By reducing the temperature of the softener to 25 F. and applying the softener in such chilled condition the available time for assembly of the shoe parts is increased to about 22 seconds, an increase of almost 100%. It is important to note that such increase in available assembly time in many instances represents the difference between failure and success, representing as it frequently does a sufiicient, as distinguished from an insuflicient, period of time in which to perform the operations incident to bringing the shoe parts together under pressure. Moreover, in employing the above softening composition, even in chilled condition, it has been found that the sole attaching pressure need not be maintained for a period greater than about 5 minutes. Thus, it will be seen that the combined advantages of sufficiently long assembly time and relatively short pressureapplying time are obtained.

While my invention has been described with particular reference to pyroxylin cements, it should be noted that the same may be practiced in connection with other cellulose derivative cements by the employment of solvent material suitable thereto.

It will thus be seen that by my invention I have provided a relatively simple method in accordance with which volatile solvents may be employed to soften pyroxylin and other cellulose derivative cements whereby in sole attaching the sole attaching pressure need be applied only for a very shorttime while yet permitting ample time for assembly of the shoe parts without premature volatilization of the solvent material.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of joining shoe parts by means of cellulose derivative cement wherein hardened cement on one or both shoe parts is activated with a solvent and the shoe parts then assembled and placed under attaching pressure, characterized by employing a solvent of such high volatility that the attaching pressure need be maintained for only a'few minutes, and cooling said volatile solvent well below room temperature, thereby retarding its volatilization for a suflicient period to provide ample time for assembling the shoe parts and placing them under pressure.

2. In the attachment of soles to shoe uppers by means of-ceilulose derivative cement wherein hardened cement on at least one of the shoe Parts is softened with a solvent and the shoe parts subsequently assembled and placed under sole attaching pressure, the step which comprises applying to the hardened cement on one of said shoe parts volatile solvent material chilled to a temperature well below that of the room whereby volatilization of the solvent prior to the ap plication of sole attaching pressure is retarded.

3. That improvement in methods of attaching soles to shoe uppers by means of cellulose derivative cement wherein the cement is applied to the sole and shoe bottom and permitted to dry and sole and shoe bottom and permitted to dry and subsequently the hardened cement is activated with a solvent, which comprises chilling said solvent and the sole substantially below normal room temperature to provide ample assembly time, applying the chilled solvent to the hardened cement on the chilled sole, assembling the sole and the shoe upper, and placing them under sole attaching pressure.

5. In the cement attaching of soles to shoe uppers wherein hardened pyroxylin cement on the sole is softened and the sole and shoe bottom brought into juxtaposition under sole attaching pressure, that improvement which comprises chilling a softening composition having a boiling point of from about 30 to C. to a temperature below the freezing point of water and applying said softening composition at its reduced temperature -to the hardened cement on the sole whereby ample assembly time is provided and whereby the sole attaching pressure need be maintained for only a very few minutes.

' I FRED C. EASTMAN. 

